February 4, 2004
Opportunity
Sees Tiny Spheres in Martian Soil
NASA's Opportunity has examined its first
patch of soil in the small crater where the rover landed on Mars
and found strikingly spherical pebbles among the mix of particles
there.
"There are features in this soil unlike
anything ever seen on Mars before," Dr. Steve Squyres, principal
investigator for the science instruments on the two Mars Exploration
Rovers, said.
Mars Under a Microscope
Click
for larger image
Courtesy NASA/JPL/US Geological Society
For better understanding of the soil, mission
controllers at NASA's Jet Propulsion Laboratory, Pasadena, Calif.,
plan to use Opportunity's wheels later this week to scoop a trench
to expose deeper material. One front wheel will rotate to dig
the hole while the other five wheels hold still.
The spherical particles appear in new pictures
from Opportunity's microscopic imager, the last of 20 cameras
to be used on the two rover missions. Other particles in the
image have jagged shapes.
Dr. Ken Herkenhoff of the U.S. Geological
Survey's Astrogeology Team said that the different of shapes
and colors indicate that the particles came from a variety of
sources.
The shapes by themselves don't reveal the
particles' origin with certainty. According to Dr. Hap McSween,
a rover science team member, a number of basic geological processes
can yield round shapeds including accretion under water. But
he added that apparent pores in the particles make the alternative
possibilities of meteor impacts or volcanic eruptions more likely
origins.
A new mineral map of Opportunity's surroundings,
the first ever done from the surface of another planet, shows
that concentrations of coarse-grained hematite vary in different
parts of the crater. The soil patch in the new microscopic images
is in an area low in hematite. The map shows higher hematite
concentrations inside the crater in a layer above an outcrop
of bedrock and on the slope just under the outcrop.
Hematite usually forms in association with
liquid water, so it holds special interest for the scientists
trying to determine whether the rover landing sites ever had
watery environments possibly suitable for sustaining life. The
map uses data from Opportunity's miniature thermal emission spectrometer,
which identifies rock types from a distance.
"We're seeing little bits and pieces
of this mystery, but we haven't pieced all the clues together
yet," Squyres said.
Opportunity's Mössbauer spectrometer,
an instrument on the rover's robotic arm designed to identify
the types of iron-bearing minerals in a target, found a strong
signal in the soil patch for olivine. Olivine is a common ingredient
in volcanic rocks. Scientists say a few days of analysis may
be needed to discern whether any fainter signals are from hematite.
Opportunity is scheduled to drive about
3 meters (10 feet) tomorrow, taking it about halfway to an area
with more hematite. On Friday it will dig a trench with one of
its front wheels, according to JPL's Dr. Mark Adler, mission
manager.
Opportunity's twin rover, Spirit, today
is reformatting its flash memory, a preventive measure that had
been planned for earlier in the week. "We spent the last
four days in the testbed testing this," Adler said. "It's
not an operation we do lightly. We've got to be sure it works
right." Tomorrow, Spirit will resume examining a rock called
Adirondack after a two-week interruption by computer memory problems.
Controllers plan to tell Spirit to brush dust off of a rock and
examine the cleaned surface tomorrow.
Each martian day, or "sol," lasts
about 40 minutes longer than an Earth day. Spirit begins its
33rd sol on Mars at 2:43 a.m. Thursday, Pacific Standard Time.
Opportunity begins its 13th sol on Mars at 3:04 p.m. Thursday,
PST.
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